Lignocellulosic feedstocks (e.g. lignocellulosic biomass) comprise mainly cellulose, hemicelluloses, and lignin. Lignocellulosic feedstocks typically are obtained from renewable resources, such as agriculture, forests, and refineries associated therewith and are not considered to be food sources. In view of these aspects, lignocellulosic feedstocks are considered desirable for the production of biofuels, chemicals, and polymers.
Existing methods delignify lignocellulosic feedstocks before entering the cellulose conversion process using solvents or other chemicals. In such delignification processes, complex equipment typically is required, which is expensive to operate because of solvent or chemical usage. In other existing processes, the conversion of lignocellulosic biomass in pretreatment and hydrolysis steps requires high temperatures to fully or partially solubilize the lignin present. Upon cooling, the lignin precipitates from solution, which may be recovered from the process and burned for thermal energy or used in other product applications. Furthermore, in certain temperature ranges the lignin becomes sticky and tends to foul the process equipment to the point of making the process inoperable.
Thus, despite existing methods, there continues to be a need for improved methods for processing lignocellulosic feedstocks, including economical recovery of lignin, with reduced fouling of the reactor tanks or vessels.